Systems and Methods Involving Multiple Torque Paths for Gas Turbine Engines

ABSTRACT

Systems and methods involving multiple torque paths of gas turbine engines are provided. In this regard, a representative spool assembly for a gas turbine engine, which incorporates a compressor, a turbine and a gear assembly, includes: a shaft operative to be driven by the turbine; a first spool segment operative to couple the shaft to the compressor; and a second spool segment operative to couple the shaft to the gear assembly. The first spool segment and the second spool segment are not coupled to each other.

BACKGROUND

1. Technical Field

This disclosure generally relates to gas turbine engines.

2. Description of the Related Art

A gas turbine engine typically incorporates a spool that mechanicallyinterconnects rotating components of a turbine with rotating componentsof a corresponding compressor. In order to accommodate axial loads ofthe spool, one or more thrust bearings typically are provided.Unfortunately, mechanical failure of a spool forward of the thrustbearing can decouple the load provided by the fan and compressor fromthe turbine, thereby resulting in an overspeed of the turbine. Such anoverspeed can be severe enough to cause turbine disks and blades to failstructurally. Specifically, structural failure of a turbine disk cancause the disk to break into multiple pieces and depart the engine bypenetrating a casing that surrounds the turbine. In order to alleviatethis concern, turbine disks and associated blades oftentimes aredesigned to accommodate such overspeed conditions resulting in the useof heavier, more robust components.

SUMMARY

Systems and methods involving multiple torque paths of gas turbineengines are provided. In this regard, an exemplary embodiment of amethod for reducing overspeed potential of a turbine of a gas turbineengine comprises: providing a first load to the turbine via a firsttorque path; providing a second load to the turbine via a second torquepath; and operating the turbine such that: mechanical failure of acomponent defining at least a portion of the first torque path does notinhibit the second load from being applied to the turbine via the secondtorque path; and mechanical failure of a component defining the secondtorque path does not inhibit the first load from being applied to theturbine via the first torque path.

An exemplary embodiment of a spool assembly for a gas turbine engine,which includes a compressor, a turbine and a gear assembly, comprises: ashaft operative to be driven by the turbine; a first spool segmentoperative to couple the shaft to the compressor; and a second spoolsegment operative to couple the shaft to the gear assembly. The firstspool segment and the second spool segment are not coupled to eachother.

An exemplary embodiment of a gas turbine engine comprises: a turbine; ashaft operative to be driven by the turbine; a compressor; a first spoolsegment coupling the shaft to the compressor; a gear assembly; a secondspool segment coupling the shaft to the gear assembly; and a fanoperative to be driven by the gear assembly. The first spool segment isoperative to transfer torque from the shaft to the compressor and not tothe gear assembly; and the second spool segment is operative to transfertorque from the shaft to the gear assembly and not to the compressor.

Other systems, methods, features and/or advantages of this disclosurewill be or may become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features and/oradvantages be included within this description and be within the scopeof the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale. Moreover, in the drawings, like reference numeralsdesignate corresponding parts throughout the several views.

FIG. 1 is a schematic diagram depicting an embodiment of a systeminvolving multiple torque pads.

FIG. 2 is a schematic diagram of the embodiment of FIG. 1, showingrepresentative regions of potential mechanical failure.

FIG. 3 is a schematic diagram depicting another embodiment of a systeminvolving multiple torque paths.

FIG. 4 is a flowchart depicting functionality of an embodiment of asystem involving multiple torque paths.

DETAILED DESCRIPTION

Systems and methods involving multiple torque paths for gas turbineengines are provided. In this regard, several exemplary embodiments willbe described. In particular, these embodiments incorporate the use ofmultiple torque paths, e.g., two such paths, that are used to transfertorque from the turbine of a gas turbine engine to other components. Forexample, one of the torque paths can be used for transferring torque toa compressor, while the another torque path can be used for providingtorque to a gearbox, which is used to rotate a fan. Notably, use ofseparate torque paths can potentially prevent an overspeed condition ofa turbine when one or more components defining one of the torque pathsmechanically fails. That is, even if one of the torque paths experiencesa mechanical failure that uncouples a load from the turbine, thecomponent being driven by the other of the torque paths still provides aload to the turbine. In some embodiments, this ability to preventturbine overspeed potentially allows for use of less robust, andoftentimes lighter, components in the turbine which can result inimproved gas turbine engine efficiency.

Referring now in more detail to the drawings, FIG. 1 is a schematicdiagram depicting an exemplary embodiment of a system involving multipletorque paths. As shown in FIG. 1, system 100 is generally configured asa geared turbofan gas turbine engine that incorporates a compressor 102,a combustion section 104, a turbine 106 (e.g., a high pressure turbine)and a shaft 108. The shaft 108 is mechanically coupled to rotatingcomponents of the turbine, including turbine disks (such as turbine disk112) and associated blades (such as blades 114).

From the turbine, shaft 108 extends forward to the compressor. However,in contrast to gas turbine engines that include a single torque path foreach spool, two torque paths are provided forward of a thrust bearing116. In particular, system 100 includes a first torque path or spoolsegment 120 and a second torque path or spool segment 122. The spoolsegments 120, 122 interconnect with the shaft at an intersection 124located adjacent to thrust bearing 116. Notably, the thrust bearingaccommodates axial loads of the shaft and prevents movement of the shaftin an aft direction, i.e., toward the turbine, if the first and secondspool segments were to fail.

Spool segment 120 is mechanically coupled to the compressor. That is,the first spool segment is mechanically coupled to compressor 130, whichincludes blades (e.g., blade 132). Notably, vanes (e.g., vein 134) areinterposed between the rotating sets of compressor blades.

Spool segment 122 is mechanically coupled to a gearbox 138. Gearbox 138is used to provide torque to a gear-driven fan 140.

An electronic engine control (EEC) 150 also is provided. The EEC 150receives inputs corresponding to engine operating parameters andprovides corresponding outputs for controlling operation of the gasturbine engine. Although desirable, it should be noted that the EEC maynot be able to adequately control rotating speed of a turbine responsiveto a total failure of a spool forward of a thrust bearing. In contrastto a spool that provides a single torque path from the turbine forwardof a thrust bearing, the embodiment of FIG. 1, however, potentiallyalleviates this situation by dividing the torque provided by the turbinebetween multiple torque paths; in this case, first and second torquepaths.

In this regard, reference is made to the schematic diagram of FIG. 2,which identifies three general areas of spool 108 that may be subjectedto mechanical failure. In particular, FIG. 2 depicts location A (locatedaft of thrust bearing 116), location B (located along spool segment120), and location C (located along spool segment 122). Notably,mechanical failure of the spool at location A causes the portion of thespool aft of the failure to move axially aft. As such, the turbineblades tend to clash with the adjacent vanes. Although resulting inturbine failure, such blade clashing may reduce a tendency of theturbine to overspeed to the point of turbine disk liberation.

In contrast, mechanical failure of the first spool segment 120 (locationB) results in load of the gearbox and the gear-driven fan being appliedvia the second spool segment 122 to the turbine. Similarly, mechanicalfailure of the second spool segment 122 (location C) results in load ofthe compressor being applied via the first spool segment 120 to theturbine. Since at least a portion of the normal operating load is stillapplied to the turbine via a remaining torque path despite failure ofone of the spool segments, the EEC may have adequate time to respond toany sensed failure. As such, the EEC may be able to provide outputs toreduce the rotational speed of the turbine, thereby potentially avoidinga critical overspeed.

FIG. 3 is a schematic diagram of another embodiment of a systeminvolving multiple torque paths. In particular, FIG. 3 schematicallydepicts a portion of a gas turbine engine 300 including a shaft 302, acompressor 304, a first torque path 306, a second torque path 308 and athrust bearing 310. Note that the rotating components of the gas turbineare shaded to visually distinguish those components from othercomponents of the gas turbine.

In operation, torque is provided from a turbine (not shown) tocompressor 304 via shaft 302 and torque path 306. Additionally, torqueis provided from the turbine to a gearbox (not shown) via shaft 302 andtorque path 308. Note that the torque path 306 diverges from torque path308 at an intersection 312, which is located in a vicinity of the thrustbearing 310.

FIG. 4 is a flowchart depicting functionality of an embodiment of asystem involving multiple torque paths. Specifically, FIG. 4 depicts anembodiment of a method for reducing overspeed potential of a powerturbine of a gas turbine engine. In this regard, the functionality (ormethod) may be construed as beginning at block 402, in which a firstload is provided to the turbine via a first torque path. In someembodiments, the first load can be associated with a compressor of thegas turbine engine. In block 404, a second load is provided to theturbine via a second torque path. In some embodiments, the second loadcan be associated with a gear assembly of the gas turbine engine. Inblock 406, the turbine is operated such that: mechanical failure of acomponent defining at least a portion of the first torque path does notinhibit the second load from being applied to the turbine via the secondtorque path; and mechanical failure of a component defining the secondtorque path does not inhibit the first load from being applied to theturbine via the first torque path.

It should be emphasized that the above-described embodiments are merelypossible examples of implementations set forth for a clear understandingof the principles of this disclosure. Many variations and modificationsmay be made to the above-described embodiments without departingsubstantially from the spirit and principles of the disclosure. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the accompanying claims.

1. A gas turbine engine comprising: a turbine; a shaft operative to bedriven by the turbine; a compressor; a first spool segment coupling theshaft to the compressor; a gear assembly; a second spool segmentcoupling the shaft to the gear assembly; and a fan operative to bedriven by the gear assembly; wherein the first spool segment isoperative to transfer torque from the shaft to the compressor and not tothe gear assembly; and wherein the second spool segment is operative totransfer torque from the shaft to the gear assembly and not to thecompressor.
 2. The gas turbine engine of claim 1, wherein: the turbineis located aft of the compressor; and the engine further comprises athrust bearing engaging the shaft and operative to inhibit aft movementof the shaft.
 3. The gas turbine engine of claim 2, wherein the thrustbearing is located aft of the first spool segment and the second spoolsegment.
 4. The gas turbine engine of claim 2, wherein the thrustbearing is located adjacent an intersection of the first spool segment,the second spool segment and the shaft.
 5. The gas turbine engine ofclaim 2, wherein, in operation and responsive to mechanical failure ofthe shaft aft of the thrust bearing, portions of the turbine driven bythe shaft move aft and contact vanes of the turbine.
 6. The gas turbineengine of claim 1, further comprising: a casing annularly surroundingthe turbine; and an electronic engine control operative to receiveinputs corresponding to engine operating parameters and to provideoutputs to control operation of the engine, the electronic enginecontrol being further operative to configure the outputs to reducerotational speed of the turbine responsive to a failure of at least oneof the first spool segment and the second spool segment such that aportion of the turbine does not penetrate the casing.
 7. The gas turbineengine of claim 1, wherein the second spool segment is operative to loadthe turbine despite a mechanical failure of the first spool segment. 8.The gas turbine engine of claim 1, wherein the first spool segment isoperative to load the turbine despite a mechanical failure of the secondspool segment.
 9. The gas turbine engine of claim 1, wherein the turbineis a high pressure turbine.
 10. The gas turbine engine of claim 1,wherein the engine is a turbofan gas turbine engine.
 11. A spoolassembly for a gas turbine engine having a compressor, a turbine and agear assembly, the spool assembly comprising: a shaft operative to bedriven by the turbine; a first spool segment coupled to the shaft andoperative to apply a load from the compressor to the shaft; and a secondspool segment coupled to the shaft and operative to apply a load fromthe gear assembly to the shaft; wherein the first spool segment and thesecond spool segment are not coupled to each other.
 12. The spoolassembly of claim 11, wherein the first spool segment is operative totransfer torque from the shaft to the compressor and not to the gearassembly.
 13. The spool assembly of claim 11, wherein the second spoolsegment is operative to transfer torque from the shaft to the gearassembly and not to the compressor.
 14. The spool assembly of claim 11,further comprising a thrust bearing operative to engage the shaft. 15.The spool assembly of claim 14, wherein the thrust bearing is operativeto engage the assembly adjacent an intersection of the first spoolsegment, the second spool segment and the shaft.
 16. The spool assemblyof claim 14, wherein the thrust bearing is operative to engage theassembly aft of the first spool segment and the second spool segment.17. A method for reducing overspeed potential of a turbine of a gasturbine engine comprising: providing a first load to the turbine via afirst torque path; providing a second load to the turbine via a secondtorque path; and operating the turbine such that: mechanical failure ofa component defining at least a portion of the first torque path doesnot inhibit the second load from being applied to the turbine via thesecond torque path; and mechanical failure of a component defining thesecond torque path does not inhibit the first load from being applied tothe turbine via the first torque path.
 18. The method of claim 17,wherein, in providing the first load, the first load is associated witha compressor.
 19. The method of claim 17, wherein, in providing thesecond load, the second load is associated with a gear-driven fan. 20.The method of claim 17, further comprising enabling portions of theturbine driven by the shaft to move aft and contact vanes of the turbineresponsive to mechanical failure of the shaft aft of the thrust bearing.